lib/blockchain.py

   1 #!/usr/bin/env python
   2 #
   3 # Electrum - lightweight Bitcoin client
   4 # Copyright (C) 2012 thomasv@ecdsa.org
   5 #
   6 # This program is free software: you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation, either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with this program. If not, see <http://www.gnu.org/licenses/>.
  18
  19
  20 import threading, time, Queue, os, sys, shutil
  21 from util import user_dir, appdata_dir, print_error
  22 from bitcoin import *
  23
  24
  25 class Blockchain(threading.Thread):
  26
  27     def __init__(self, config, network):
  28         threading.Thread.__init__(self)
  29         self.daemon = True
  30         self.config = config
  31         self.network = network
  32         self.lock = threading.Lock()
  33         self.height = 0
  34         self.local_height = 0
  35         self.running = False
  36         self.headers_url = 'http://headers.electrum.org/blockchain_headers'
  37         self.set_local_height()
  38         self.queue = Queue.Queue()
  39         self.servers_height = {}
  40
  41
  42     def stop(self):
  43         with self.lock: self.running = False
  44
  45
  46     def is_running(self):
  47         with self.lock: return self.running
  48
  49
  50     def run(self):
  51         self.init_headers_file()
  52         self.set_local_height()
  53         print_error( "blocks:", self.local_height )
  54
  55         with self.lock:
  56             self.running = True
  57
  58         while self.is_running():
  59
  60             try:
  61                 result = self.queue.get()
  62             except Queue.Empty:
  63                 continue
  64
  65             if not result: continue
  66
  67             i, result = result
  68             if not result: continue
  69
  70             header = result.get('result')
  71             height = header.get('block_height')
  72             self.servers_height[i.server] = height
  73
  74             if height > self.local_height + 50:
  75                 self.get_chunks(i, header, height)
  76                 self.network.trigger_callback('updated')
  77
  78             if height > self.local_height:
  79                 # get missing parts from interface (until it connects to my chain)
  80                 chain = self.get_chain( i, header )
  81
  82                 # skip that server if the result is not consistent
  83                 if not chain: continue
  84
  85                 # verify the chain
  86                 if self.verify_chain( chain ):
  87                     print_error("height:", height, i.server)
  88                     for header in chain:
  89                         self.save_header(header)
  90                         self.height = height
  91                 else:
  92                     print_error("error", i.server)
  93                     # todo: dismiss that server
  94
  95                 self.network.trigger_callback('updated')
  96
  97             h = self.servers_height.get(self.network.interface.server)
  98             if h is not None and h < height - 1:
  99                 print "server is lagging", height, h
 100                 self.network.interface.stop()
 101
 102
 103
 104
 105     def verify_chain(self, chain):
 106
 107         first_header = chain[0]
 108         prev_header = self.read_header(first_header.get('block_height') -1)
 109
 110         for header in chain:
 111
 112             height = header.get('block_height')
 113
 114             prev_hash = self.hash_header(prev_header)
 115             bits, target = self.get_target(height/2016)
 116             _hash = self.hash_header(header)
 117             try:
 118                 assert prev_hash == header.get('prev_block_hash')
 119                 assert bits == header.get('bits')
 120                 assert eval('0x'+_hash) < target
 121             except:
 122                 return False
 123
 124             prev_header = header
 125
 126         return True
 127
 128
 129
 130     def verify_chunk(self, index, hexdata):
 131         data = hexdata.decode('hex')
 132         height = index*2016
 133         num = len(data)/80
 134
 135         if index == 0:
 136             previous_hash = ("0"*64)
 137         else:
 138             prev_header = self.read_header(index*2016-1)
 139             if prev_header is None: raise
 140             previous_hash = self.hash_header(prev_header)
 141
 142         bits, target = self.get_target(index)
 143
 144         for i in range(num):
 145             height = index*2016 + i
 146             raw_header = data[i*80:(i+1)*80]
 147             header = self.header_from_string(raw_header)
 148             _hash = self.hash_header(header)
 149             assert previous_hash == header.get('prev_block_hash')
 150             assert bits == header.get('bits')
 151             assert eval('0x'+_hash) < target
 152
 153             previous_header = header
 154             previous_hash = _hash
 155
 156         self.save_chunk(index, data)
 157         print_error("validated chunk %d"%height)
 158
 159
 160     def verify_header(self, header):
 161         # add header to the blockchain file
 162         # if there is a reorg, push it in a stack
 163
 164         height = header.get('block_height')
 165
 166         prev_header = self.read_header(height -1)
 167         if not prev_header:
 168             # return False to request previous header
 169             return False
 170
 171         prev_hash = self.hash_header(prev_header)
 172         bits, target = self.get_target(height/2016)
 173         _hash = self.hash_header(header)
 174         try:
 175             assert prev_hash == header.get('prev_block_hash')
 176             assert bits == header.get('bits')
 177             assert eval('0x'+_hash) < target
 178         except:
 179             # this can be caused by a reorg.
 180             print_error("verify header failed"+ repr(header))
 181             verifier.undo_verifications()
 182
 183             # return False to request previous header.
 184             return False
 185
 186         self.save_header(header)
 187         print_error("verify header:", _hash, height)
 188         return True
 189
 190
 191     def header_to_string(self, res):
 192         s = int_to_hex(res.get('version'),4) \
 193             + rev_hex(res.get('prev_block_hash')) \
 194             + rev_hex(res.get('merkle_root')) \
 195             + int_to_hex(int(res.get('timestamp')),4) \
 196             + int_to_hex(int(res.get('bits')),4) \
 197             + int_to_hex(int(res.get('nonce')),4)
 198         return s
 199
 200
 201     def header_from_string(self, s):
 202         hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
 203         h = {}
 204         h['version'] = hex_to_int(s[0:4])
 205         h['prev_block_hash'] = hash_encode(s[4:36])
 206         h['merkle_root'] = hash_encode(s[36:68])
 207         h['timestamp'] = hex_to_int(s[68:72])
 208         h['bits'] = hex_to_int(s[72:76])
 209         h['nonce'] = hex_to_int(s[76:80])
 210         return h
 211
 212     def hash_header(self, header):
 213         return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
 214
 215     def path(self):
 216         return os.path.join( self.config.path, 'blockchain_headers')
 217
 218     def init_headers_file(self):
 219         filename = self.path()
 220         if os.path.exists(filename):
 221             return
 222
 223         try:
 224             import urllib, socket
 225             socket.setdefaulttimeout(30)
 226             print_error("downloading ", self.headers_url )
 227             urllib.urlretrieve(self.headers_url, filename)
 228         except:
 229             print_error( "download failed. creating file", filename )
 230             open(filename,'wb+').close()
 231
 232     def save_chunk(self, index, chunk):
 233         filename = self.path()
 234         f = open(filename,'rb+')
 235         f.seek(index*2016*80)
 236         h = f.write(chunk)
 237         f.close()
 238         self.set_local_height()
 239
 240     def save_header(self, header):
 241         data = self.header_to_string(header).decode('hex')
 242         assert len(data) == 80
 243         height = header.get('block_height')
 244         filename = self.path()
 245         f = open(filename,'rb+')
 246         f.seek(height*80)
 247         h = f.write(data)
 248         f.close()
 249         self.set_local_height()
 250
 251
 252     def set_local_height(self):
 253         name = self.path()
 254         if os.path.exists(name):
 255             h = os.path.getsize(name)/80 - 1
 256             if self.local_height != h:
 257                 self.local_height = h
 258                 self.height = self.local_height
 259
 260
 261     def read_header(self, block_height):
 262         name = self.path()
 263         if os.path.exists(name):
 264             f = open(name,'rb')
 265             f.seek(block_height*80)
 266             h = f.read(80)
 267             f.close()
 268             if len(h) == 80:
 269                 h = self.header_from_string(h)
 270                 return h
 271
 272
 273     def get_target(self, index):
 274
 275         max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
 276         if index == 0: return 0x1d00ffff, max_target
 277
 278         first = self.read_header((index-1)*2016)
 279         last = self.read_header(index*2016-1)
 280
 281         nActualTimespan = last.get('timestamp') - first.get('timestamp')
 282         nTargetTimespan = 14*24*60*60
 283         nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
 284         nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
 285
 286         bits = last.get('bits')
 287         # convert to bignum
 288         MM = 256*256*256
 289         a = bits%MM
 290         if a < 0x8000:
 291             a *= 256
 292         target = (a) * pow(2, 8 * (bits/MM - 3))
 293
 294         # new target
 295         new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
 296
 297         # convert it to bits
 298         c = ("%064X"%new_target)[2:]
 299         i = 31
 300         while c[0:2]=="00":
 301             c = c[2:]
 302             i -= 1
 303
 304         c = eval('0x'+c[0:6])
 305         if c > 0x800000:
 306             c /= 256
 307             i += 1
 308
 309         new_bits = c + MM * i
 310         return new_bits, new_target
 311
 312
 313     def request_header(self, i, h, queue):
 314         print_error("requesting header %d from %s"%(h, i.server))
 315         i.send([ ('blockchain.block.get_header',[h])], lambda i,r: queue.put((i,r)))
 316
 317     def retrieve_header(self, i, queue):
 318         while True:
 319             try:
 320                 ir = queue.get(timeout=1)
 321             except Queue.Empty:
 322                 print_error('timeout')
 323                 continue
 324
 325             if not ir:
 326                 continue
 327
 328             i, r = ir
 329
 330             if r.get('error'):
 331                 print_error('Verifier received an error:', r)
 332                 continue
 333
 334             # 3. handle response
 335             method = r['method']
 336             params = r['params']
 337             result = r['result']
 338
 339             if method == 'blockchain.block.get_header':
 340                 return result
 341
 342
 343
 344     def get_chain(self, interface, final_header):
 345
 346         header = final_header
 347         chain = [ final_header ]
 348         requested_header = False
 349         queue = Queue.Queue()
 350
 351         while self.is_running():
 352
 353             if requested_header:
 354                 header = self.retrieve_header(interface, queue)
 355                 if not header: return
 356                 chain = [ header ] + chain
 357                 requested_header = False
 358
 359             height = header.get('block_height')
 360             previous_header = self.read_header(height -1)
 361             if not previous_header:
 362                 self.request_header(interface, height - 1, queue)
 363                 requested_header = True
 364                 continue
 365
 366             # verify that it connects to my chain
 367             prev_hash = self.hash_header(previous_header)
 368             if prev_hash != header.get('prev_block_hash'):
 369                 print_error("reorg")
 370                 self.request_header(interface, height - 1, queue)
 371                 requested_header = True
 372                 continue
 373
 374             else:
 375                 # the chain is complete
 376                 return chain
 377
 378
 379     def get_chunks(self, i, header, height):
 380         requested_chunks = []
 381         queue = Queue.Queue()
 382         min_index = (self.local_height + 1)/2016
 383         max_index = (height + 1)/2016
 384         for n in range(min_index, max_index + 1):
 385             print_error( "requesting chunk", n )
 386             i.send([ ('blockchain.block.get_chunk',[n])], lambda i,r:queue.put(r))
 387             requested_chunks.append(n)
 388             break
 389
 390         while requested_chunks:
 391             try:
 392                 r = queue.get(timeout=1)
 393             except Queue.Empty:
 394                 continue
 395             if not r: continue
 396
 397             if r.get('error'):
 398                 print_error('Verifier received an error:', r)
 399                 continue
 400
 401             # 3. handle response
 402             params = r['params']
 403             result = r['result']
 404
 405             index = params[0]
 406             self.verify_chunk(index, result)
 407             requested_chunks.remove(index)
 408
 409
 410
 411
 412
 413
 414